1. Field of the Invention
The submitted invention relates to a micromechanically fabricated read/write head for charge storage devices and a method for its manufacture.
2. Description of Prior Art
Based on the scanning tunnel or scanning powered microscope, a series of new types of storage processes have been proposed, such as a nitride-oxide-silicon (NOS) storage device, comprising a silicon substrate, and superimposed thin layers of oxide and nitride. In such a storage device, a charge is inscribed into the thin nitride film with the help of a fine tip. By applying an electrical pulse between the tip and silicon substrate, a charge flows through tunnels through the thin oxide layer into the nitride, and is fixed there. This can be referred to as a writing procedure. The information can also be read again or cancelled with the same tip. With storage elements of this type, storage densities of 30 Gbits/in.sup.2 have been achieved in trials with charge surface units of about 150 nm diameter. The available writing and reading structures, and also those inserted, were actually developed as inductive magnetic read/write heads, and thus are not optimally suitable for insertion in NOS storage devices. Their complex construction hardly allows any further reduction of the active read/write surfaces. On grounds of the large lateral dimensions of about 12 mm.times.600 .mu.m, an arrangement with several read/write heads cannot be realized, which however would be desirable in view of an improved data rate by parallel processing.
A storage device with an arrangement of several read/write heads is described in the U.S. Pat. No. 5,307,311 issued to John W. Sliwa, Jr. The storage device taught therein comprises several cantilevers which store bits, and read/write heads which are located opposite the cantilevers. The read/write heads strongly resemble the tips very strongly in their structure for the scanning tunnel or scanning powered microscopy. By this shape of the tip, through frequent direct contact with the surface of a charge storage device in long term operation, it leads to signs of wear on the tips, resulting in an altered supporting surface, so that the used tip presses with another force on the surface of a charge storage device, in comparison with a perfectly new tip.
It, therefore, can be seen that there is a need for a read/write head for a charge storage device which has a tip capable of reading and writing information in contact with the surface of the charged storage device over long term operation with minimal wear.